1. Field of the Invention
The present invention relates to a propeller shaft used in a vehicle such as a motor vehicle or the like, and more particularly to a propeller shaft provided with a dynamic damper and a paper damper in an inner portion.
2. Description of the Related Art
As shown in FIG. 7, there has been conventionally known a propeller shaft 100 structured such that a dynamic damper 102 and a paper damper 104 are provided in an inner portion (for example as disclosed in patent document 1). In other words, an output of an internal combustion engine mounted to a front portion of a vehicle is generally transmitted to a drive wheel in a rear side by the propeller shaft 100 via a transmission, however, since a characteristic of the propeller shaft 100 exerts a great influence on a vibration of the vehicle, it is possible to improve a vibration characteristic of the propeller shaft 100 by installing the dynamic damper 102 to a cylinder inner portion of the propeller shaft 100 and attenuating a vibration by the dynamic damper 102.
Further, a stuffy sound is generated at a time of a rotation of the propeller shaft 100, however, it is possible to reduce or vanish the stuffy sound by setting the paper damper 104 in the inner portion of the propeller shaft 100. In this case, as shown in FIG. 8, the paper damper 104 is formed as an approximately rectangular shape in a plan view in a state of being expanded, and is inserted to the inner portion of the propeller shaft 100 in a state of being wound in a tubular shape (for example as disclosed in patent document 2).    (Patent Document 1) Japanese Patent Application Laid-open No. 2001-12446    (Patent Document 2) Japanese Patent No. 3544579    (Patent Document 3) Japanese Patent No. 3753191
However, in the structure in which the dynamic damper and the paper damper are provided in the inner portion of the propeller shaft, a part (a weight portion or the like) of the dynamic damper may come into contact with the paper damper at a time of simultaneously inserting the dynamic damper and the paper damper to the inner portion of the propeller shaft. If the weight member of the dynamic damper comes into contact with the paper damper, a frequency characteristic of the dynamic damper is changed. Accordingly, the function of the dynamic damper is compromised.
In general, the dynamic damper is constituted by a ring-like member positioned in an outer side in a diametrical direction, and a weight member positioned in an inner side in the radial direction of the ring-like member. One method of avoiding a contact between the weight member and the paper damper is intentionally elongating a length in an axial direction of the ring-like member. However, if the length in the axial direction of the ring-like member is elongated, the dynamic damper is enlarged in size so as to increase its weight, and there is generated the other problem that a manufacturing cost is increased.